Can't make Qt look in project directory for db.

So I have a project which reads info from a sqlite3 DB. If I point the full path (C:\Users\bla\Desktop\myPrjFolder\myDB.3db) it works but if I point the absolute path (I think is called) \myDB.3db it doesn't. I also tried via a resource file :prefix/myDB.3db still doesn't works. I need to do this so the project can be portable.